Apparatus and method for scalable power distribution

ABSTRACT

According to one aspect of the invention, a plug-in module is provided for installation in a power distribution assembly. In one embodiment, the plug-in module includes a housing, an electrical isolation and overcurrent protection device located in the housing and a current sensing device located in the housing and adapted to sense a current carried by the electrical isolation and overcurrent protection device. The plug-in module may further include a power cable including a first end that is pre-terminated at the plug-in module to connect the power cable to the electrical isolation and overcurrent protection device, and electrical contacts adapted to removably couple the plug-in module to a plurality of stationary electrical conductors of the power distribution assembly. According to one embodiment, the electrical isolation and overcurrent protection device includes a circuit breaker.

RELATED APPLICATIONS

This application is a divisional of, and claims priority under 35 U.S.C.§ 120 and § 121 to co-pending U.S. patent application Ser. No.11/455,227 entitled “Apparatus and Method for Scalable PowerDistribution,” filed on Jun. 16, 2006, which is herein incorporated byreference in its entirety.

BACKGROUND OF INVENTION

1. Field of Invention

Embodiments of the invention relate generally to electrical powerdistribution equipment. More specifically, at least one embodimentrelates to an apparatus and a method for scalable power distribution.

2. Discussion of Related Art

Centralized data centers for computer, communications and otherelectronic equipment have been in use for a number of years. Morerecently, with the increasing use of the Internet, large scale datacenters that provide hosting services for Internet service providers(“ISPs”), application service providers (“ASPs”) and Internet contentproviders are becoming increasingly popular. Typical centralized datacenters contain numerous racks of equipment that require power, coolingand connections to communication facilities.

In general, centralized data centers have a power distribution systemconfigured to avoid power outages because the data centers include ahigh percentage of critical loads without which an enterprise may beunable to operate. Often, an uninterruptible power supply (“UPS”) isemployed in the power distribution system to ensure that equipmentreceives continuous power and avoids any power outages. Typical powerdistribution systems include racks of equipment, for example, serversand the like that are located in the data center. Generally, a pluralityof power distribution circuits are provided where each circuit suppliespower to one or more electrical loads (e.g., servers, cooling systems,lighting circuits, etc.) via a circuit breaker. These systems generallyinclude racks in which the circuit breakers are installed (i.e., powerdistribution units) or alternatively racks that include an electricalpanel board which is in general similar in design to the panel boardsthat are found in ordinary commercial facilities.

Problems with these approaches include the fact that the installation orremoval of a circuit breaker from the panel board or power distributionunit requires that a skilled individual (i.e., an electrician) performthe installation or removal in close proximity to energized electricalcircuits which may include exposed electrical connections and/orconductors. Alternatively, the power distribution equipment can bede-energized to facilitate the installation or removal of one or morecircuit breakers. Of course, given the critical nature of the electricalload in the data centers, even these scheduled outages are undesirable.

Some existing approaches attempt to minimize power interruptionsresulting from the connection of new power distribution circuits byproviding pre-fabricated plug-in power cables whereby a first end of thecable includes a connector that can be plugged into an output of acircuit breaker at the power distribution unit and a second end that canbe connected to an electrical load. Although this approach may allow anelectrical load to be safely connected to the circuit breaker withoutde-energizing the entire power distribution unit (e.g., connected withthe panel board energized but without requiring any “hot work”), itrequires that the cable lengths be pre-determined. In addition, suchsystems may not be scalable, that is, each panel board or other powerdistribution unit may not be configured for the correct size or quantityof circuits and corresponding circuit breakers.

As one alternative, some current systems allow a user to order apreconfigured power distribution unit that includes a main breaker witha fixed rating and a plurality of branch circuit breakers each with apre-selected current rating. Given the dynamic nature of the electricalload that may be included in the data center, for example, the additionof one or more computers, servers, chillers, etc., the precedingapproach does not provide an advantage except in the rare instance wherethe power distribution unit supplies a known, fixed electrical load.That is, the preceding approach is only effective where the designerand/or user of the distribution system can accurately identify theelectrical loading and power distribution requirements of the facilityat the time of installation. Generally, it is unrealistic to expect thatthe designer and/or user will accurately predict the electrical loading(e.g., the quantity of distribution circuits and their maximum loading)given the dynamic nature of facility design, power distribution systemsand the connected electrical load. As a result, preconfigured powerdistributions are often specified with substantial excess capacity thatis never used.

SUMMARY OF INVENTION

In one or more embodiments, the invention provides a modular, scalablepower distribution system that provides plug-in modules that may besafely installed and removed without disrupting other electricalcircuits connected to the power distribution unit. As a result, in someembodiments, the invention provides for a scalable power distributionapparatus that provides flexibility to meet the changing electricalneeds of a facility such as a data center. In still other embodiments,the invention provides a system with a limited set of components thatmay be universally applied to a wide variety of applications.

According to one aspect of the invention, a plug-in module is providedfor installation in a power distribution assembly. In one embodiment,the plug-in module includes a housing, an electrical isolation andovercurrent protection device located in the housing and a currentsensing device located in the housing and adapted to sense a currentcarried by the electrical isolation and overcurrent protection device.The plug-in module may further include a power cable including a firstend that is pre-terminated at the plug-in module to connect the powercable to the electrical isolation and overcurrent protection device, andelectrical contacts adapted to removably couple the plug-in module to aplurality of stationary electrical conductors of the power distributionassembly. According to one embodiment, the electrical isolation andovercurrent protection device includes a circuit breaker. In a furtherembodiment, the power cable is pre-terminated inside the housing. In yetanother embodiment, the circuit breaker is adapted for mounting on a DINrail. In still another embodiment, the plug-in module includes amechanical stress relief device for the power cable.

According to another aspect of the invention, a power distributionapparatus includes a plug-in module and a bus bar assembly. In oneembodiment, the plug-in module includes a housing, a circuit breakerlocated in the housing, a power cable including a first end that ispre-terminated at the plug-in module to connect the cable to the circuitbreaker, and electrical contacts adapted to removably couple the plug-inmodule to a plurality of bus bars. According to one embodiment, the busbar includes the plurality of bus bars, an insulated rear panel, a firstside panel and a second side panel where the insulated rear panel, thefirst side panel and the second side panel are sized and arranged toform a region adapted to receive the plug-in module. In one embodiment,the region is free of uninsulated conductors.

In accordance with one embodiment, the bus bar assembly includes atleast one guide element included with at least one of the first sidepanel and the second side panel. In a version of this embodiment, theplug-in module includes at least one guide element sized and adapted toengage the at least one guide element of the bus bar assembly. In oneembodiment, the bus bar assembly further includes a plurality of openingformed in the insulated rear panel where the openings are sized andadapted to allow insertion of the electrical contacts within theopenings, and the at least one guide element is sized and adapted toengage a part of the plug-in module such that each of the electricalcontacts is aligned with a corresponding one of the plurality ofopenings, respectively.

In accordance with another aspect, the invention provides a method ofinstalling a power distribution system in a facility. According to oneembodiment, the method includes an act of obtaining a plurality ofplug-in modules where each of the plug-in modules includes a housingcontaining the circuit breaker. In addition, in one embodiment, theplug-in module includes a power cable having a first end electricallycoupled to the circuit breaker, and electrical contacts coupled to thecircuit breaker. The method further includes an act of installing atleast some of the plurality of plug-in modules in a power distributionassembly by sliding the plug-in modules into the power distributionassembly such that the electrical contacts of each of the plug-inmodules are electrically coupled to electrical conductors in the powerdistribution assembly.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1 illustrates a block diagram of an electrical system in whichscalable power distribution equipment is employed in accordance with oneembodiment of the invention;

FIG. 2 illustrates an isometric view of a plug-in module in accordancewith one embodiment of the invention;

FIG. 3 illustrates a plan view of a plug-in module in accordance withone embodiment of the invention;

FIG. 4 illustrates an isometric view of the plug-in module of FIG. 3 inaccordance with one embodiment of the invention;

FIG. 5 illustrates a plug-in module installed in a bus bar assembly inaccordance with one embodiment of the invention;

FIG. 6 illustrates a top view of a plug-in module installed in a bus barassembly in accordance with an embodiment of the invention;

FIG. 7 illustrates a plug-in module in accordance with anotherembodiment of the invention;

FIG. 8 illustrates a plug-in module in accordance with yet anotherembodiment of the invention;

FIG. 9 illustrates a bus bar assembly and plug-in modules in accordancewith a further embodiment of the invention;

FIG. 10 illustrates a bus bar assembly and plug-in modules in accordancewith a still further embodiment of the invention;

FIG. 11 illustrates a bus bar assembly, plug-in modules and a switchingpanel in accordance with an embodiment of the invention;

FIG. 12 illustrates a block diagram of a bus bar assembly and plug-inmodules in accordance with an embodiment of the invention;

FIG. 13 illustrates a plan view of a plug-in module installed in a busbar assembly in accordance with an embodiment of the invention; and

FIG. 14 illustrates an isometric view of a plug-in module in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION

This invention is not limited in its application to the details ofconstruction and the arrangement of components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways. Also, the phraseology and terminology used hereinis for the purpose of description and should not be regarded aslimiting. The use of “including,” “comprising,” or “having,”“containing”, “involving”, and variations thereof herein, is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items.

FIG. 1 illustrates a power distribution system 10 in accordance with oneembodiment, where the system includes a power distribution unit 11(“PDU”) that provides a plurality of output circuits 18 (e.g., branchcircuits) to supply electrical power to a plurality of electrical loads,for example, loads found in a data center or another type of facility.The power distribution system 10 may include an input circuit breaker13, a transformer 14, an uninterruptible power supply (“UPS”) 15, abypass switch 16, a bus bar assembly 12 and monitoring and controlcircuitry 17. In various embodiments, the PDU 11 includes the bus barassembly 12 while each of the remaining apparatus listed in thepreceding sentence may either be included in the PDU 11, or optionally,be physically located elsewhere in the power distribution system 10.

According to one embodiment, the PDU 11 includes the bus bar assembly 12and each of the input circuit breaker 13, the transformer 14, the UPS15, the bypass switch 16 and the monitoring and control circuitry 17, asillustrated in FIG. 1. In another embodiment, each of the input circuitbreaker 13, the transformer 14, the UPS 15, the bypass switch 16 and atleast a part of the monitoring and control circuitry 17 are locatedexternal to the PDU 11. In other embodiments, various combinations ofthe input circuit breaker 13, the transformer 14, the UPS 15, the bypassswitch 16 and the monitoring and control circuitry 17 are co-locatedwith the bus bar assembly 12 in the PDU 11. Thus, in one embodiment, thebus bar assembly 12, the input circuit breaker 13, the transformer 14,the bypass switch 16 and at least a part of the monitoring and controlcircuitry 17 are located in the PDU 11 while the UPS is located externalto the unit 11. In yet another embodiment, the power distribution system10 does not include a UPS. As a result, in one embodiment, the PDU 11includes the bus bar assembly 12 and each of the input circuit breaker13, the transformer 14, and at least a part of the monitoring andcontrol circuitry 17, while the UPS 15 and the bypass switch 16 are notemployed with the PDU 11.

According to one embodiment, the PDU 11 is contained within an equipmentrack that allows the “rack mounting” of the bus bar assembly 12 andothers of the apparatus included within it. In a version of thisembodiment, the PDU 11 is included in a row of equipment racks that maybe coupled to one another as is well known to those of ordinary skill inthe art. As a result, in some embodiments, the PDU 11 includes the busbar assembly 12, while one or more other equipment racks include othersof the input circuit breaker 13, the transformer 14, the UPS 15, thebypass switch 16 and the monitoring and control circuitry 17. Inversions of these embodiments, the equipment racks including theapparatus identified here are coupled together to form a row ofequipment racks employed in the power distribution system 10, forexample, as described in commonly assigned U.S. Pat. No. 6,967,283,entitled “Adjustable Scalable Rack Power System and Method,” issued Nov.22, 2005 to Neil Rasmussen et al. which is incorporated by referenceherein. The above-described configurations describe only some of thepossible configurations and are not intended to be limiting.

In accordance with one embodiment, the bus bar assembly 12 is adapted toreceive at least one plug-in module that may include a switching deviceand overcurrent protection (e.g., an electrical isolation andovercurrent protection device), for example, a circuit breaker, a fusedswitch, or a separate switch and one or more fuses. In one embodiment,the plug-in module is installed in the bus bar assembly 12 to connectthe bus bar assembly to the output circuits. As is described in greaterdetail below, in various embodiments, the plug-in module may include apre-terminated power cable to facilitate a safe connection of new outputcircuits with the PDU 11 and the bus bar assembly energized. Further, invarious embodiments, the bus bar assembly 12 provides a region free ofuninsulated conductors in which the plug-in module is installed.

In one embodiment, the bus bar assembly 12 includes a plurality ofpositions A-H that are each adapted to receive a plug-in module. In aversion of this embodiment, the bus bar assembly is rated for a maximumcontinuous current of 400 Amps while each position A-H is rated for amaximum continuous current of 100 Amps. In one embodiment, each of theplug-in modules is also rated for 100 Amps although various ampacitycircuit breakers may be included in the plug-in modules, e.g., havingampacities of from less than 1 Amp up to and including a maximum of 100Amps. Such an approach may, in various embodiments, provide a scalablesystem that can employ two elements (i.e., a bus bar assembly andplug-in modules) to meet a wide variety of the existing and futureelectrical needs of a facility. This results in efficiencies inmanufacturing, supply chain and operation and maintenance for theequipment. For example, a manufacturer need not manufacture and adesigner need not try to select from a plurality of semi-customequipment. Accordingly, the equipment may have a lower cost and greateravailability.

As illustrated in FIG. 1, a source of input power is connected to theline side of the input circuit breaker 13, the load side of the inputcircuit breaker 13 is connected to a line side (i.e., the input) of thetransformer 14, the load side (i.e., the output) of the transformer 14is connected to the input of the bypass switch 16, and the output of thebypass switch 16 is connected to the bus bar assembly 12. In oneembodiment, both the input and the output of the UPS 15 are connected tothe bypass switch 16. As is well known by those of ordinary skill in theart, the bypass switch 16 operates to selectively connect the output ofthe bypass switch 16 to either the transformer 14 or the UPS 15. Inaccordance with one embodiment, the bus bar assembly 12 receives thepower from the bypass switch 16 and supplies power to one or more outputcircuits 18. In one embodiment, the bypass switch is adapted toselectively couple the output of the transformer 14 and the output ofthe UPS 15 to the bus bar assembly 12.

The monitoring and control circuitry 17 may perform solely monitoringfunctions, solely control functions or a combination of monitoring andcontrol. In various embodiments, monitoring includes any one or anycombination of the following functions and/or the following functionsand additional functions: current sensing, power monitoring (e.g.,energy consumption), circuit on/off sensing, bypass switch status, UPSstatus and the like. Any of the preceding may be accompanied by signalprocessing employed for the purpose of monitoring and/or control. Forexample, current and voltage signals may be processed to determineenergy consumption. Accordingly, the monitoring and control circuitry 17may include one or more processors, e.g., microprocessors.

In addition, the monitoring and control circuitry 17 may includecommunications with any of the various components included in the PDU11. Accordingly, in some embodiments, the PDU includes circuitry (notshown) that connects the monitoring and control circuitry 17 to one ormore of the bus bar assembly 12, input circuit breaker 13, thetransformer 14, the UPS 15, and the bypass switch 16. Further, invarious embodiments, the monitoring and control circuitry 17 may beincluded in or communicate with a local area network and or a wide areanetwork (e.g., the Internet).

In further embodiments, control functions include any one or anycombination of the following functions and/or the following functionsand/or additional functions: control of UPS operation, control of bypassswitch operation, operation of one or more circuit breakers, otherswitching operations and the like. Accordingly, the monitoring andcontrol circuitry 17 may include a user interface such as a displayand/or switches, meters, indicating lights, and the like.

Referring now to FIG. 2, an isometric view of a plug-in module 20 inaccordance with one embodiment of the invention is illustrated. Ingeneral, the plug-in module 20 is employed to supply power from the PDU11 to an electrical load. Further, in accordance with variousembodiments of the invention, the plug-in module 20 includes a switchingdevice such that a line-side of the plug-in module connects to a sourceof electrical power and a load side of the plug-in module 20 can bedirectly connected to an electrical load or connected to furthercircuitry that is connected to the electrical load. Thus, in oneembodiment, the plug-in module 20 includes a circuit breaker that canprovide electrical isolation and overcurrent protection (e.g., aminiature molded case circuit breaker that senses overloads and/or shortcircuits). In other embodiments, the plug-in module includes acombination of an isolation switch and fusing such as a fused disconnectswitch or a combination of a switch and fuses that are separate from oneanother. In accordance with one embodiment, the plug-in module is sizedand adapted for installation in a bus bar assembly, for example, the busbar assembly 42 illustrated in FIG. 5. In various embodiments, theplug-in module 20 includes a power cable 21 which may include an endthat is pre-terminated at the plug-in module 20.

As used herein, the term “pre-termination” refers to the fact that afirst end of the power cable 21 is connected at the plug-in module 20before the plug-in module arrives on a job site. According to oneembodiment, the pre-termination is performed during the manufacture ofthe plug-in module 20.

In some embodiments, the length of the power cable 21 is alsoestablished during manufacture. That is, in one embodiment, a pluralityof commonly used fixed lengths of power cable 21 may be available. In aversion of this embodiment, the plurality of commonly used fixed lengthsare established based on a distance between a first enclosure and/orequipment rack and a second enclosure and/or equipment rack. Thus, aconnection between the plug-in module 20 and an immediately adjacentequipment rack may require a shorter length of cable when compared withthe length of cable required for a connection between the plug-in module20 and a more distant equipment rack. Because equipment racks are oftensupplied in standard sizes the length of the power cables 21 can bedetermined in advance. In addition, a second end of the power cable 21may include a connector to facilitate the connection of the power cable21 to an electrical load.

As illustrated in FIG. 2, the plug-in module 20 includes a housing 22having a top panel 23, a front panel 24 and a first side panel 26. Invarious embodiments, the plug-in module 20 may also include a bottompanel, a rear panel and a second side panel (located opposite the first)which are not illustrated in FIG. 2. The housing 22 may be manufacturedusing any rigid material (conductive material or insulating material)suitable for use with electrical equipment, for example, the housing maybe manufactured from steel. In some embodiments, portions of the housingare conductive while other portions of the housing are insulating.According to one embodiment, a first extension 28 extends from the firstside panel 26 in a substantially perpendicular direction while a secondextension 30 may extend from the second side panel.

In various embodiments, the plug-in module 20 may include additionalfeatures and various combinations of features. For example, according toone embodiment, the plug-in module 20 includes a handle 32 that isattached to the housing 22 (e.g., at the front panel 24) which may beemployed by a user to install and remove the plug-in module 20. In someembodiments, the plug-in module 20 includes a latch 33 that secures theplug-in module 20 in a fully installed position. In the illustratedembodiment, the latch 33 is attached to an end of the first extension28. Alternatively, a single latch 33 may be attached to an end of thesecond extension 30. In yet another embodiment, a separate latch 33 maybe attached to each of the first extension 28 and the second extension30.

In addition, one or more of the housing 22 and/or extensions 28, 30 mayinclude a rejection feature to provide an interference employed toprevent the installation of a plug-in module 20 based on one or moreconditions, for example, where a nominal voltage rating of the plug-inmodule 20 is lower than a nominal voltage rating of equipment (e.g., thebus bar assembly) in which the plug-in module is being installed, wherethe plug-in module is being installed up-side down, etc.

The plug-in module 20 may also include a guide element 36 which mayassist in properly aligning the plug-in module 20 when it is beinginstalled. For example, the guide element 36 may engage a correspondingpart of an enclosure/rack or bus bar assembly in which the plug-inmodule 20 is being installed. The guide element 36 may be an integralpart of the housing or a separate component. In addition, a plurality ofguide elements 36 may be employed. In one embodiment, the guide element36 is a rail located on the side panel 26 of the housing 22. In thisembodiment, the guide element 36 may engage a corresponding groove in,for example, a bus bar assembly. In a further embodiment, a separateguide element 36 is included on each of the side panels. It should beapparent to those of ordinary skill in the art that the guide element orelements 26 may include structure other than a rail, for example, a tabor an extension (such as a cylindrical extension) may be employed.Further, the guide element may be located anywhere on the plug-in module20 that will facilitate a proper alignment of the module. It should alsobe apparent that the guide element 36 need not extend from the plug-inmodule but may instead be a groove, channel, tube, hollow or otherrecess that engages corresponding structure extending from the bus barassembly, enclosure and/or rack in which the plug-in module 20 isinstalled.

The latch 33 may include a variety of different structure that allowsthe plug-in module 20 to be retained in a fully-installed position,e.g., with the plug-in module 20 fully connected to the bus bar assembly42. For example, the latch 33 may have a range of motion such that thelatch 33 deflects from an at-rest position as the plug-in module 20 isinstalled and then captures (or is captured by) a part of the bus barassembly and/or rack in which it is installed. As should be apparent toone of ordinary skill in the art, the latch 33 can be manufactured fromflexible material and/or rigid material configured to flex in an elasticmanner when pressure is applied to the latch 33.

As mentioned above, the plug-in module 20 may include a circuit breaker34 such that the plug-in module 20 can provide overcurrent protectionfor the electrical load to which it is connected, e.g., it can provideoverload and short circuit protection. In one embodiment, the circuitbreaker 34 is located such that at least a part of the circuit breakeris accessible with the housing 22 completely assembled. For example, thefront panel 24 may include an opening through which the face of thecircuit breaker 34 is accessible and/or extends. Such a configurationcan allow the circuit breaker status (i.e., open, closed, tripped, etc.)to be determined and also allow operating personnel to operate thecircuit breaker 34.

In one embodiment, the circuit breaker 34 is a Pro-M series miniaturecircuit breaker manufactured by ABB. Example part numbers for IEC ratedcircuit breakers include: S201-K16; S201-K32; S203-K16; and S203-K32.Example part numbers for circuit breakers designed to meet traditionalU.S. standards include: S201U-K20; S203U-K32; and S203U-K50. In anotherembodiment, the circuit breaker 34 is a L-Series miniature circuitbreaker manufactured by Altech. Examples include a Catalog No. 1CU02Lrated for 0.2 Amps and single pole applications and a Catalog No. 3CU63Lrated for 63 Amps and three pole applications. It should be apparent tothose of ordinary skill in the art that other makes, models andconfigurations (e.g., four pole, six pole, etc.) can be employed. Inaddition, the plug-in module 20 can include a circuit breaker thatcomplies with any applicable standard from any of a variety of standardsetting bodies.

As illustrated, the power cable 21 is pre-terminated within the housing22, however, in an alternate embodiment the power cable 21 ispre-terminated external to the housing 22. Further, where the powercable 21 is pre-terminated to the plug-in module 20, the pre-terminationprovides a connection between one or more of the conductors included inthe power cable 21 and the circuit breaker 34. In accordance with oneembodiment, the pre-termination results in the power cable 21 beingdirectly connected to one or more terminals/lugs integral with thecircuit breaker 34. However, such a direct connection is not requiredand various other configurations may be employed. For example, the powercable 21 may be terminated at another terminal point/lug located in theplug-in module 20. In this embodiment, a jumper or short piece of cable,wire, etc. may connect the terminal point/lug (and as a result the powercable) to the circuit breaker 21.

The plug-in module 20 may also include various control elements toprovide status indications and/or allow control of, for example, thecircuit breaker 34. According to one embodiment, the plug-in module 20includes one or more status indication lights that may be located in thefront panel 24 and used to indicate a circuit breaker status. In anotherembodiment, the plug-in module 20 may include a relay that can beemployed to open the circuit breaker to disconnect the load beingsupplied by the plug-in module 20 as part of a load shedding scheme. Inaddition, the circuit breaker or other isolating means may beelectrically operated such that is can be electrically opened, closedand reset. The plug-in module 20 may also include an auxiliary switch orone or more voltage sensors to determine the position of the poles ofthe circuit breaker, the status of switch contacts or the status offuses.

Further, the plug-in module 20 may also include one or more temperaturesensors to provide data concerning, for example, the temperature ofcontacts that connect the plug-in module 20 to the bus bar assembly 12,the temperature of circuit breaker and/or the temperature of the circuitbreaker terminals/lugs. In some embodiments, the preceding approach maybe employed to reduce or eliminate the need to perform IR scanning forover temperature conditions. In one embodiment, the preceding approachprovides data that is employed to supplement IR scanning, for example,to identify areas of interest.

FIG. 3 illustrates a plan view of the plug-in module 20 of FIG. 2 withthe top of the housing (e.g., a top panel) removed. A second side panel27 and a rear panel 40 included as part of the housing 22 areillustrated in FIG. 3. In addition to the housing 22, the power cable 21and the circuit breaker 34, e.g., a molded case circuit breaker, theplug-in module 20 includes line conductors 52, a neutral conductor 54, aground conductor 56 and a plurality of contacts 58. In accordance withone embodiment, the power cable 21 includes each of the line conductors52, the neutral conductor 54, and the ground conductor 56. In oneembodiment, additional line conductors 59 connect the circuit breaker 34to the contacts 58. Further, in one embodiment, each line conductor 59is ultrasonically welded to the corresponding contact of the pluralityof contacts 58. As should be apparent to those of ordinary skill in theart, other configurations of the power cable may be employed, forexample, the power cable 21 may not include a neutral when the plug-inmodule 20 is connected to a 3-wire load. As illustrated in FIG. 3, insome embodiments, the power cable 21 may have the line conductors 52pre-terminated at the circuit breaker while the neutral conductor 54 andthe ground conductor 56 are terminated elsewhere in the plug-in module20.

In accordance with one embodiment, the plug-in module 20 includes amechanical stress relief device 57 for the power cable 21. That is, theplug-in module 20 includes a device to reduce any forces that may tendto pull the pre-terminated power cable 21 from the plug-in module 20.According to one embodiment, the mechanical stress relief device 57includes an internal bushing, an external bushing, other hardware, or acombination of any of the preceding. In one embodiment, the mechanicalstress relief device 57 is a type of stress relief device that is alsosuitable for use with twist lock cord end connectors. In a version ofthis embodiment, the mechanical stress relief 57 is a strain reliefdevice provided by Hubbell Incorporated, for example, a model that isapproved by Underwriter's Laboratory. According to one embodiment, themechanical stress relief 57 is overmolded onto the power cable 21 wherethe power cable 21 includes three single phase power cords.

In addition, in one embodiment, the plurality of contacts 58 are locatedoutside the housing proximate the rear panel 40. In one embodiment, eachof the electrical contacts include a pair of contact “fingers” sized andadapted to engage a bus bar with a proper amount of tension to create astable electrical connection when the plug-in module 20 is inserted inthe bus bar assembly 42, e.g., the contacts provide sufficient pressureto prevent the connection with the bus bar from overheating when currentis being carried by the plug-in module. As should be apparent, otherconfigurations of the plurality of contacts 58 may be employed so longas the contacts 58 are adapted to removably engage correspondingstationary contacts and/or contact surfaces. Stationary conductors,stationary contacts and stationary contact surfaces have fixed positionsthat cannot be moved when the PDU is in service, i.e., when the PDU isenergized. In the illustrated examples, a bus bar can be a stationaryconductor that provides a stationary contact surface. In a version ofthis embodiment, the neutral conductor 54 and the ground conductor 56are pre-terminated at the corresponding contacts 58, respectively.According to one embodiment, the contacts 58 are manufactured fromcopper with a 2-3 micron coating of nickel and a tin plating finish. Ina further embodiment, contact pressure is assisted by a spring clip, forexample, a spring clip manufactured from carbon steel or stainlesssteel.

In one embodiment, the plug-in module 20 also includes a plurality ofcurrent sensing devices 62, for example, current transformers (“CTs”).According to one embodiment, the plug-in module 20 includes a separatecurrent sensing device 62 for each line conductor. Thus, according toone embodiment, the plug-in module 20 is employed with a three phasecircuit and includes three CTs. Of course, other configurations may beused, for example, the plug-in module may also include a fourth CT forsensing neutral current. A wide variety of current sensing devices maybe employed provided that they include a suitable current rating andphysical dimensions that allow them to be installed within the housing22 of the plug-in module 20. Example current sensors include: a part no.5304 from Amecon Inc.; a part no. T75001 from Falco Electronics, LTD.;and a part no. 460-1001A from Shilchar-payton Technologies, LTD.

In accordance with one embodiment, the plug-in module 20 includes aconnector 64 sized and adapted for connecting one or more secondarycircuits to circuitry located external to the plug-in module 20 when theplug-in module is installed in the bus bar assembly 42. Secondarycircuits can include any monitoring and/or control circuits includingcircuits that employ the output of the current sensors. Accordingly, theconnector 64 may be employed to connect secondary circuits or portionsthereof included in the plug-in module 20 to secondary circuitryincluded in the monitoring and control circuitry 17.

In various embodiments, the connector 64 includes at least one contactwhich is configured to engage a corresponding contact (not shown)included in the bus bar assembly. As should be apparent to those ofordinary skill in the art, that various styles and types of contacts maybe employed provided that the contacts and connector are rated for thenominal operating voltage and nominal current of the secondary circuitor circuits. According to one embodiment, the connector 64 extends fromwithin the housing 22 through the rear panel 40. In one embodiment, theconnector 64 is adapted to mate with an edge connector included in thebus bar assembly 42. Example connectors include: a part no. 5-5530843-0from Tyco Electronics Corp.; and a part no. 2551-20D from Ito-ChienEnterprise Co. Ltd.

In accordance with one embodiment, a part 65 of the circuit breaker 34externally accessible (i.e., accessible outside the housing 22) isillustrated. In addition, FIG. 3 illustrates the use of the guideelement 36 (i.e., a first guide element) and a second guide element 37.

Referring now to FIG. 4, an isometric view of the plug-in module of FIG.3 is illustrated. As illustrated here, each of the three current sensors62 is clearly shown. In accordance with one embodiment, the currentsensors 62 are included on a printed circuit board (“PCB”) 66 locatedwithin the housing 22. In addition, the portion of the connector 64located within the housing 22 is illustrated. In accordance with oneembodiment, the connector 64 is also coupled to the PCB 66 within thehousing. In a version of this embodiment, at least some of the contactswithin the connector 64 are connected to circuitry located on the PCB66.

In some embodiments, the secondary circuitry located in the plug-inmodule 20 does not include a processor or any control functions, forexample, the secondary circuitry may simply provide the output of thesensing devices to the connector 64. The outputs may then becommunicated to the monitoring and control circuitry 17 via theconnector 64 when the plug-in module is installed in the bus barassembly 42. In alternate embodiments, the secondary circuitry includesa processor 68 (e.g., a microprocessor), for example, located on the PCB66. In versions of these embodiments, the processor 68 may be employedto perform either monitoring, control functions or both. Further, theprocessor 68 can be included in the monitoring and control circuitry 17when the plug-in module is installed in the PDU 11.

In one embodiment, the plug-in module 20 includes a memory 69 (e.g.,RAM, ROM, etc.) that stores information, for example, informationconcerning the plug-in module 20. The information may include theampacity of the plug-in module 20, the quantity of poles, the date ofmanufacture, the manufacturing facility, authenticity codes, the size ofthe conductors included in the power cable 21, the style of the powercable 21, the length of the power cable 21 and other information.According to one embodiment, the plug-in module 20 is programmed withthe preceding information at the time of manufacture. Further, where theplug-in module 20 communicates with a communication network (forexample, via the connector 64) the information can be employed toautomatically set up and provide information concerning the plug-inmodule 20 to a power distribution monitoring system. In one embodiment,the memory 69 is included in a chip, for example, an EPROM chip.

As mentioned previously, the plug-in module may be installed in a busbar assembly, for example, the bus bar assembly 12 located in PDU 11.Referring now to FIG. 5, a system 40 is shown in which the plug-inmodule 20 is installed in a bus bar assembly 42 at a first position,i.e. position D. In accordance with the illustrated embodiment, the busbar assembly includes a plurality of positions in which separate plug-inmodules may be installed. In the interest of clarity, only 5 of theavailable positions are uniquely identified, positions A, B, C, D, andE, with position E being the position immediately below the position inwhich the plug-in module 20 is installed, position C being above andimmediately adjacent position D and each of positions A and B beinglocated further above position D.

In one embodiment, the bus bar assembly 42 includes a plurality of busbars 43 and the plug-in module 20 is installed by sliding the moduleinto the bus bar assembly 42 to engage electrical contacts 58 at therear of the plug-in module 20 with the bus bars 43. In one embodiment,bus bar assembly includes a first side panel 44 and a second side panel45. The side panels 44, 45 may each be a single unit, or alternatively,may each include a plurality of side panels. For example, the sidepanels 45, 46 may include a separate side panel for each of theplurality of positions, e.g., the positions A-E. The side panels 44, 45may be manufactured using any rigid material (conductive material orinsulating material) suitable for use with electrical equipment, forexample, the side panels 44, 45 may be manufactured from steel. Inanother embodiment, the side panels 44, 45 are manufactured frominsulating material.

Either or both of the side panels 44, 45 may include a guide element 46that is used to properly position and guide the plug-in module 20 as itis installed. In one embodiment, the guide elements 46 are slots thatare sized and adapted to engage the guide elements 36, 37 in the form ofguide rails included in the plug-in module 20. As described previouslywith respect to the guide elements 36, a wide variety of structure maybe employed to provide the guide elements 46 so long as they are sizedand adapted to engage corresponding structure included in the plug-inmodule 20.

The bus bar assembly 42 may also include a rear panel 48 that providesan electrically insulating barrier between the region where the plug-inmodule(s) are located and the location of the bus bars 43. In oneembodiment, the rear panel 48 is made of plastic. In accordance with oneembodiment, the rear panel 48 includes a plurality of openings 50 thatare sized and adapted to allow the electrical connection to be made withthe plug-in module 20 but are small enough to prevent the accidentalcontact of a user and/or hand tools with the bus bar. Accordingly, inone embodiment, the rear panel 48 and the side panels 44, 45 form aregion that is free of uninsulated conductors. As a result, the plug-inmodules 20 may be safely installed and removed from the bus bar assembly42 while the bus bars are energized. In one embodiment, the powerdistribution unit includes a cable guide and securing system thatprovide hardware for securely locating the power cables 21 for aplurality of plug-in modules 20 installed in the bus bar assembly, forexample, using wire-ties. In one embodiment, the cable guide andsecuring system is included as part of the bus bar assembly 42.

In addition, embodiments of the bus bar assembly 42 also allow the powercable 21 to be safely routed with the bus bar energized. For example,where the bus bar assembly 42 is installed in an enclosure and/orequipment rack the separate cables 21 associated with each of aplurality of plug-in modules 20 may be safely routed within theenclosure/rack (e.g., on the front side of the bus bar assembly) whileothers of the plug-in modules are in service and supplying power to oneor more output circuits. In one embodiment, the enclosure includesbushings and/or glands through which the power cables 21 exit theenclosure, e.g., dust-proof, weather-proof, etc. In various embodiments,the power cables 21 may exit the rack and/or enclosure via a roof or afloor. In one embodiment, a power cable 21 associated with a firstplug-in module exits through the roof and a power cable 21 associatedwith a second plug-in module exits through the floor of the same rackand/or enclosure.

In some embodiments, the rear panel 48 includes a connector 68 that canbe employed to connect the monitoring and control circuitry 17, or aportion thereof, to secondary circuitry included in the plug-in module20.

Referring now to FIG. 6, a plan view of the plug-in module 20 connectedto the bus bar assembly 42 is illustrated in accordance with oneembodiment. The bus bar assembly 42 includes the plurality of bus bar43, for example, a bus bar for each of the line conductors, the neutral,and the ground. The bus bars 43 may be separated by insulators 66, forexample, cylindrically shaped insulators that may be stacked betweenadjacent bus bar or between a bus bar and an adjacent side panel.According to one embodiment, the insulators are held in place usingscrews, although other fastening means may be employed. FIG. 6 alsoillustrates the connector included with the plug-in module 20 (e.g., theconnector 64) engaged with the connector 68 included in the bus barassembly 42. For example, in the illustrated embodiment, the connector64 is received within the connector 68 when the plug-in module 20 isinstalled in the bus bar assembly 42. When the connectors 64, 68 areengaged as described here, at least one contact included in theconnector 64 is coupled with at least one contact included in theconnector 68. As is apparent to those of ordinary skill in the art, eachof the connectors 64, 68 may include a plurality of contacts that areengaged when the plug-in module 20 is installed. Further, in theillustrated embodiment, the connector 68 is coupled to control circuitrylocated on a printed circuit board 70 included with the bus bar assembly42.

FIG. 6 also illustrates the connection of the plurality of contacts 58to the corresponding bus bar 43. That is, as the plug-in module 20 isslid into a position (e.g., one of the positions A-E) within the bus barassembly 42, each of the contacts 58 penetrate through the correspondingopening 50 in the rear panel 48 and engage the corresponding bus bar 43.According to one embodiment, the contacts 58 are contact fingers thatare spread slightly apart (relative to their relaxed state) when theyengage the bus bar 43. When the plug-in module is fully engaged one ofthe contacts 58 is fully engaged with each of the corresponding bus bars43.

In one embodiment, the plug-in module 20 is installed by a user whograsps the handle 32 and aligns the guide element or elements of theplug-in module 20 with the corresponding guide element(s) of the bus barassembly 42. Once the corresponding guide elements are initially engagedthe user can continue to grip the handle 32 and apply pressure to slidethe plug-in module 20 further into the bus bar assembly until thecontacts 58 fully engage the corresponding bus bar 43. At this point,the connectors 64 and 68 are also fully engaged. In some embodiments,the latch 33 provides an indication that the plug-in module 20 is fullyinstalled. The preceding process may be reversed (beginning with theunlatching of the latch 33, if included) to remove the plug-in module20.

A second end (not shown) of the power cable 21 may be connected to anelectrical load or further circuitry that is connected to an electricalload either before or after the plug-in module 20 is installed in thebus bar assembly 42. In either instance, the circuit breaker 34 is inthe open position, for safety reasons, during the installation ofplug-in module 20. Once the plug-in module 20 is installed and thesecond end of the power cable 21 terminated, the circuit breaker 34 canbe closed, for example, to supply power to power cable 21 and thecircuitry that is connected to it.

The plug-in module 20 may be provided in a variety of configurations,i.e., the housing 22 need not have a square or rectangular overallshape. FIG. 7 illustrates one such alternate configuration in which thehousing 22 includes an additional face 71. According to one embodiment,the power cable 21 enters the housing 22 at the face 71. In a version ofthis embodiment, the mechanical strain relief 57 is included at the face71. In some embodiments, the face 71 is positioned at an angle such thatthe power cable 21 exits the plug-in module 20 at an angle that is notperpendicular to the adjacent side panel 44, 45. As a result, in theseembodiments, the power cable 21 may exit the housing 22 at a rearwardswept angle that allows the power cable 21 to be more easily routedwithin the enclosure.

According to one embodiment, the plug-in module 20 includes many of thepreceding features described herein including the handle 32, the circuitbreaker 34, the guide elements 36, 37, the plurality of contacts 58, thecurrent sensors 62 and the connector 64. According to the illustratedembodiment, the connector 64 is an edge connector. The embodimentillustrated in FIG. 7 also illustrates a circuit breaker operator 67 anda first opening 63 that provides external access to the operator 67 toallow the circuit breaker to be manually opened, closed and/or reset. Inaddition, the opening 63 may allow operating personnel to determine thestatus (i.e., open, closed, tripped) of the circuit breaker 34. FIG. 7also illustrates second openings 72 in the housing that, in oneembodiment, allows the re-torquing of mechanical connections within thehousing 22 without the need to disassemble the housing 22. According toone embodiment, the second openings 72 align with the terminals/lugs ofthe circuit breaker 34 to allow the connections of the line conductorsto be installed, checked and/or tightened.

The plug-in module 20 may include single pole circuit breakers or multipole circuit breakers in various embodiments. In some embodiments, thecircuit breaker is a three pole circuit breaker while in otherembodiments, the circuit breaker is a six pole circuit breaker.

The power cable 21 may also include a variety of embodiments dependingupon the load that is being supplied by the plug-in module 20. Forexample, the plug-in module 20 may supply either a single phase load,multiple single phase loads or three phase load. In addition, the secondend of the power cable 21 (i.e., the end that is not pre-terminated) mayinclude a connector. FIG. 8 illustrates one such embodiment where aplug-in module 20 includes a power cable 21 that is split into aplurality of branch cables 21A, 21B, and 21C. In one embodiment, theplug-in module 20 is a three phase module and the power cable 21includes conductors for all three phases. In a further embodiment,however, three single pole circuit breakers (e.g., three circuitbreakers 34) are included in the plug-in module and the power cable 21is split into the three branch cables where the first branch cable 21Aincludes a single phase supplied by one single pole breaker, the secondbranch cable 21B includes another single phase supplied by anothersingle pole breaker, and the third branch cable 21C includes theremaining single phase supplied by the third single pole breaker. Theimmediately preceding approach can save space by allowing three separatebranch circuits to be supplied via a single plug-in module.

In one embodiment, each of the three branch cables 21A, 21B, 21Cincludes a connector 78 that can be plugged into an equipment rack. Inanother version, the power cable includes a three phase connector. Anyof a variety of connectors may be employed including NEMA L21-20, L5,L6, L14, and L15 connectors, type CS50 connectors, IEC309 pin andsleeves devices, etc.

The preceding architecture may be employed to supply equipment racksthat are adjacent a PDU in which the plug-in module 20 is installed. Inone embodiment, the power cable 21 is connected to a three phaseequipment rack (i.e., a rack that includes three phase load). In anotherembodiment, the first branch cable 21A is connected to a first equipmentrack, the second branch cable 21B is connected to a second equipmentrack, and the third branch cable 21C is connected to a third equipmentrack where each of the first, second and third equipment racks aresingle phase equipment racks (i.e., racks that only require single phasepower.)

Further, the power cable 21 may be supplied in fixed lengths that areestablished when the equipment is ordered, for example, where thedimensions of a plurality of equipment racks with which the plug-inmodule 20 is employed are known, a pre-determined length may beaccurately determined for the power cable 21 that is to connect theplug-in module 20 to equipment in another rack.

FIG. 12 illustrates an embodiment that employs a plurality of adjacentequipment racks including a first rack 74A which includes a bus barassembly 42 and plug-in modules 20. One or more additional equipmentracks are also included, i.e., a second rack 74B, a third rack 74C and afourth rack 74D. According to one embodiment, one or more of the racks74B, 74C and 74D include electrical load that is supplied power via theplug-in module 20. In a further embodiment, the first rack 74A includesa UPS that supplies power to the bus bar assembly 42. As a result, theload supplied via each of the plug-in modules 20 is also supplied powerfrom the UPS.

In accordance with one embodiment, the plug-in modules 20 includepre-terminated power cables 21 which may each include a connector 78.For example, the equipment racks 74B, 74C and 74D may each includesingle phase load that are connected to the plug-in modules 20 via thecables 21A, 21B and 21C, respectively. Alternatively, or in combinationwith the preceding, one or more of the cables 21A, 21B and 21C maysupply polyphase power (e.g., three phases) to one or more of theequipment racks 74B, 74C and 74D.

Each of connectors 78A, 78B and 78C may connect the power cable 21 to apower cable 80A, 80B, and 80C associated with one of the equipment racks74B, 74C and 74D, respectively. Thus, in some embodiments, the powercables 80A, 80B and 80C complete the electrical connection between theplug-in modules 20 and the equipment rack that is receiving power fromthe plug-in modules 20. In addition, the connectors 78A, 78B and 78C maybe connected to a corresponding connector (not illustrated) attached tothe end of the power cables 80A, 80B and 80C.

FIG. 12 illustrates one example of a power distribution systemarchitecture employing the bus bar assembly 42 and plug-in modules 20,however, various embodiments of the invention support otherconfigurations. Additional equipment, for example, UPS batteries may beincluded in the equipment rack 74A. In some embodiments, the powercables 21 may be connected to remote equipment racks. Further, theremote equipment racks may include an additional bus bar assembly andplug-in modules. That is, in one embodiment, a plug-in module in a firstbus bar assembly may supply power to a second bus bar assembly. Inanother embodiment, a bus bar assembly and plug-in modules may belocated in an equipment rack where all the electrical load that issupplied power by the plug-in modules is located in one or more remoteequipment racks. Other combinations of the above configurations andcombinations of the above and different configurations may also beemployed.

According to various embodiments, the bus bar assembly 42 may beinstalled in a variety of configurations and orientations includingconfigurations that provide a high density of available circuits. FIG. 9illustrates one such embodiment. According to one embodiment, the busbar assembly 42 is installed in a vertical orientation in a rack 74. Inone embodiment, the rack 74 is a standard width rack (e.g., 600 mm wide)while in another embodiment the rack 74 includes a non-standard width,for example, a half rack with a width of 300 mm. In various embodiments,the bus bar assembly 42 is adapted to receive a plurality of plug-inmodules 20. In one such embodiment, the bus bar assembly 42 is sized andadapted to receive a quantity of up to 28 3-pole plug-in modules. Inaddition, where the rack 74 is a half-width rack two bus bar assemblies42 can be installed adjacent one another in a full size rack to doublethe quantity of available plug-in modules 20. In some embodiments, thepositions (e.g., the positions A-E) are spaced to provide a gap to allowfor sufficient air circulation (and heat transfer) to maintain the fullload operating temperatures of a plurality of plug-in modules 20 at orbelow a desired maximum. In one embodiment, the full load rating of thecircuit breakers included in the plug-in modules 20 are derated due tothe temperature rise expected to occur during operation.

Referring now to FIG. 10, a horizontally mounted bus bar assembly 42 isillustrated. Here too, depending upon the configuration, the bus barassembly 42 may be installed in equipment racks having any of a varietyof dimensions. In the illustrated embodiment, the bus bar assembly 42 issized and adapted to receive a plurality of plug-in modules 20 where theplug-in modules are also oriented in a 90 degree rotation relative tothe previously illustrated embodiments. This approach also allows for ahigh density of output circuits, for example, where a single equipmentrack 74 includes a plurality of horizontally mounted bus bar assemblies42.

Other equipment may also be included along with the bus bar assembly 42in an equipment rack. For example, FIG. 11 illustrates one suchembodiment in which the bus bar assembly 42 and plurality of plug-inmodules 20 are installed in an equipment rack along with a switchingpanel 76. According to one embodiment, the switching panel 76 includesan input switch, an output switch and a bypass switch associated with aUPS. In one embodiment, the UPS is located in an equipment rack that isadjacent the rack 74. In a further embodiment, modular batteriesassociated with the UPS are located in an equipment rack locatedadjacent the rack that includes the UPS on the side opposite the rack74. In one embodiment, the switching panel 76 includes three subfeedoutputs having ampacities ranging from 100 Amps to 160 Amps.

FIG. 13 illustrates a plan view of a plug-in module 20 in accordancewith one embodiment of the invention. In the illustrated embodiment, thetop of the housing is removed and, as a result, the components locatedin the interior of the housing can be seen. The plug-in module 20includes a circuit breaker 34 with an operator 83 that can be located inat least three operating positions. The operator 83 can be located in afirst operating position A where the circuit breaker is in a closedposition; a second operating position B where the circuit breaker istripped; and, a third operating position C where the circuit breaker isin an open position. According to one embodiment, the circuit breaker 34is retained within an approximately central region of the housing 22 bysupport structure 82. The support structure may be comprised of one ormore molded pieces that are sized and spaced such that they retain thecircuit breaker 34 between them when the circuit breaker 34 is locatedwithin the housing.

In accordance with one embodiment, the plug-in module 20 also includesan interlock 84 that acts to prevent the plug-in module 20 from beingconnected to or disconnected from the bus bars 43 when the circuitbreaker 34 is closed. In general, the interlock 84 operates by slidinginto engagement with the operator 83 to ensure that the circuit breaker34 is open when the plug-in module is connected or disconnected from thebus bar assembly 42. According to one embodiment, the interlock iscomprised of an interference 86, an arm 88, a tab 90 with an engagementsurface 91, and a spring 92. When the plug-in module is not installed ina bus bar assembly 42, the spring 92 biases the interlock in a directionaway from the operator 83, for example, in a direction parallel to thefront panel 24 of the housing.

In accordance with one embodiment, the interference 86 engages withcorresponding structure in the bus bar assembly 42 when the plug-inmodule 20 is either installed or removed from the bus bar assembly 42.For example, when the plug-in module 20 is installed, the interference86 is engaged by structure in the bus bar assembly (or enclosure), andas a result, the bias provided by the spring 92 is overcome and the arm88 and tab 90 slide laterally to move the engagement surface 91. Theengagement surface 91 contacts the operator 83 and moves the operator 83to position C (if the circuit breaker is not already open). Then, whenthe plug-in module 20 is in the fully-installed position (e.g., theplurality of contacts 58 are fully engaged with the bus bars 43), theinterference 86 is not engaged by the corresponding structure and thespring 92 biases the arm 88 and tab 90 back to the at rest position inwhich the engagement surface 91 does not interfere with the operation ofthe circuit breaker 34. In addition, in accordance with one embodiment,the interlock 84 also acts to open the circuit breaker 34 in a similarfashion upon removal of the plug-in module 20 from the bus bar assembly42 prior to any of the plurality of contacts disconnecting from any ofthe corresponding bus bars. That is, upon removal of the plug-in module20, the engagement surface 91 is biased into engagement with theoperator 83 (if the circuit breaker 34 is closed) before the pluralityof contacts 58 are disconnected from the bus bars 43.

In various embodiments, the interlock 84 includes structure such as aslide, a lever, an interference including a mechanical contact surfaceand/or other structure. According to one embodiment, the plug-in module20 also includes a mechanically-assisted engagement device to assistoperating personnel when they install or remove the plug-in module fromengagement with the bus bars 43. That is, in one embodiment, it may bebeneficial to provide mechanical assistance to slide the plurality ofcontacts 58 onto each of the corresponding bus bars 43, e.g., toovercome resistance to the spreading apart of the pairs of contactfingers as they engage and slide over the corresponding bus bars. Theresistance may, for example, be the result of a dimension by which thecontacts of each pair are separated and/or pressure supplied by contactsprings. When the plug-in module 20 is installed, the contacts (e.g.,the contact fingers) act to grip the bus bars 43. Thus, in oneembodiment, the mechanically assisted engagement device may also beemployed to assist during the removal of the plug-in module. Inaccordance with one embodiment, the mechanically assisted engagementdevice includes a lever and cam configured to provide a mechanicaladvantage during the installation and the removal of the plug-in modulewhile also providing the above-mentioned interlock, e.g., to open thecircuit breaker 34 before it is connected to or disconnected from thebus bars 43.

FIG. 13 also illustrates the structure of a ground contact 93 includedamong the plurality of contacts 58. In particular, in one embodiment,the ground contact 93 is sized and shaped such that the ground contact93 of the plug-in module 20 is the first of the plurality of contacts 58to engage their corresponding bus bar. For example, in one embodiment,the ground contact 93 may be longer than each of the others of theplurality of contacts 58, however, the ground contact may also beoriented differently than others of the plurality of contacts 58. In oneembodiment, the ground contact 93 engages a corresponding ground busbar; therefore, the ground contact 93 illustrated in FIG. 13 providesfor a safer operation because a ground circuit is completed prior to anyof the line conductors, or neutral conductor engaging a correspondingbus bar.

According to one embodiment, a back panel 41 is included in the bus barassembly 42. In this embodiment, the first side panel 44, the secondside panel 45, the rear panel 48, and the back panel 41 form a region 47that encloses the bus bars 43. In a version of this embodiment, thefirst side panel 44, the second side panel 45 and the back panel 41 areconstructed of sheet metal and the rear panel 48 is constructed of anelectrically insulating material. FIG. 13 also illustrates an embodimentwhere the printed circuit board 70 is located outside the region 47.

Referring now to FIG. 14, an isometric view from the underside of aplug-in module 20 is illustrated in accordance with one embodiment. FIG.14 illustrates a bottom panel 25 of the housing, the openings 72, thetab 90 and engagement surface 91, the circuit breaker operator 83(illustrated in each of 3 possible positions A, B, C), spacers 96 andventilating ports 98. In accordance with one embodiment, spacers 96assist in maintaining a desired air gap between adjacent plug-in modules20, i.e., the spacers 96 are raised areas on the bottom panel 25.According to one embodiment, the top panel of the housing can alsoinclude spacers 96. In one embodiment, the ventilating ports 98 areslots provided to allow for air circulation through the housing 11.

FIG. 14 illustrates a fixed tab 93 in accordance with one embodiment. Inthis embodiment, the tab 90 and the fixed tab 93 are sized and spaced toallow an operator to grasp the fixed tab 93 and move the tab 90 towardsthe fixed tab 93 to open or reset the circuit breaker. For example, inone embodiment, the tab 90 and the fixed tab 93 are spaced apart suchthat an operator can squeeze the tab 90 and the fixed tab 93 between athumb and forefinger to overcome the bias of the spring 92.

In various embodiments, the architecture provided by the bus barassembly 42 and the plug-in modules 20 allows for a scalable powerdistribution system that can more easily adapt to changes in theelectrical requirements of the facility (e.g., a data center) where itis installed. In particular, the architecture may allow a facility tosafely add new output circuits without the need for a power outage.

Further, in accordance with one embodiment, the architecture provides astandardized set of equipment ratings that can be employed in a widevariety of applications. As a result, manufacturers, equipment designersand facility operators can more easily and more economically supplypower distribution equipment, design scalable and adaptable powerdistribution systems, and maintain and expand power distributionsystems. That is, a very few “core” elements may be employed to supplypower to a wide variety of dynamic electrical loads.

The plug-in module 20 may include any of a variety of switching devices,however, where the plug-in module includes a circuit breaker, thecircuit breaker may have any of a wide range of continuous currentratings. This approach provides a system that is highly adaptable. Forexample, the plug-in module may be standardized for a specific maximumcontinuous current rating (e.g., 100 Amps). In one embodiment, thestandardized continuous current rating is the result of a selection ofthe plurality of contacts 58 and other conductors integral to theplug-in module, i.e., to provide hardware that is rated for a minimum of100 Amps. In addition, the sizing of the housing 22 may be selected suchthat it is sufficient to receive the largest molded case circuit breakerincluded in the available range of continuous current (e.g., 0-100Amps). According to one embodiment, the plug-in module is sized andadapted to receive circuit breakers configured for mounting on a DINrail, for example, circuit breakers with a continuous current rating offrom fractions of an Amp to 63 Amps. According to one embodiment, a DINrail is located within the housing 22 and the circuit breaker 34 ismounted on the rail. In one embodiment, the form factor across theentire range of current ratings is the same.

Various embodiments may integrate features of the plug-in module 20 intoa circuit breaker 34 (e.g., into the molded housing of a molded casecircuit breaker) such that the circuit breaker 34 can be installed inthe bus bar assembly 42 in the manner described herein for a plug-inmodule 20. For example, a circuit breaker may be equipped with aplurality of contacts 58 and the circuit breaker 34 and circuit breakerhousing may include any of or any combination of the guide element 36,the stress relief device 57, the connector 64, the handle 32, the latch33, the PCB 66, the processor 68, the memory 69 and the interlock 84. Inone embodiment, the housing 22 of the plug-in module is eliminated asdescribed here. In one embodiment, the circuit breaker 34 is sized andadapted to be directly installed in the bus bar assembly 42 without aseparate housing 22. Alternatively, some of the features described asbeing in the housing 22 may instead be included in a circuit breakerthat is installed in the housing 22 of the plug-in module 20.

The overall electrical ratings of the plug-in module 20 and the bus barassembly 42 may also be standardized to a very few ratings that eachmeet of a wide variety of applications. In some embodiments, thestandardized hardware is approved by one or more of UL, CSA and VDE. Inone embodiment, the standardized hardware includes a first set ofplug-in modules 20 and bus bar assemblies 42 rated for 208/120 Voltapplications, a second set rated for 415/240 Volt applications and athird set rated for 400/230 Volt applications. In each of the precedingembodiments, the bus bar assembly 42 may include a single standardizedcontinuous current rating of 400 Amps. As mentioned previously, such anapproach simplifies the manufacturing, distribution, selection andapplication of the power distribution equipment.

In various embodiments, the electrical isolation and overcurrentprotection may include any one of or any combination of circuitbreakers, trip elements, fuses and switchable contacts (e.g., switches).

The apparatus and systems described herein may be employed to provide ascalable and flexible power distribution system for any of a widevariety of facilities including data centers and other commercial andindustrial facilities.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

1-17. (canceled)
 18. A power distribution apparatus comprising: aplug-in module including a housing, a circuit breaker located in thehousing, a power cable including a first end that is pre-terminated atthe plug-in module to connect the cable to the circuit breaker, andelectrical contacts adapted to removably couple the plug-in module to aplurality of bus bars; and a bus bar assembly including the plurality ofbus bars, an insulated rear panel, a first side panel and a second sidepanel, wherein the insulated rear panel, the first side panel and thesecond side panel are sized and arranged to form a region adapted toreceive the plug-in module.
 19. The power distribution apparatus ofclaim 18, wherein the region is free of uninsulated conductors.
 20. Thepower distribution apparatus of claim 18, wherein the plug-in moduleincludes a current sensing device adapted to sense a current carried bythe circuit breaker.
 21. The power distribution apparatus of claim 18,wherein at least a part of the circuit breaker is accessible outside thehousing.
 22. The power distribution apparatus of claim 18, wherein busbar assembly includes at least one guide element included with at leastone of the first side panel and the second side panel.
 23. The powerdistribution apparatus of claim 22, wherein the plug-in module includesat least one guide element sized and adapted to engage the at least oneguide element of the bus bar assembly.
 24. The power distributionapparatus of claim 22, wherein the bus bar assembly further includes aplurality of openings formed in the insulated rear panel, wherein theopenings are sized and adapted to allow insertion of the electricalcontacts within the openings, and wherein the at least one guide elementis sized and adapted to engage a part of the plug-in module such thateach of the electrical contacts is aligned with a corresponding one ofthe plurality of openings, respectively.
 25. The power distributionapparatus of claim 18, wherein the plug-in module includes a secondarycircuit and at least one contact adapted to couple the secondary circuitto circuitry located in the bus bar assembly.
 26. The power distributionapparatus of claim 25, wherein the bus bar assembly includes at leastone contact included in the circuitry, and wherein the at least onecontact of the bus bar assembly is adapted to couple to the at least onecontact of the plug-in module.
 27. The power distribution apparatus ofclaim 26, wherein the at least one contact included in the plug-inmodule is included in a first connector and the at least one contactincluded in the bus bar assembly is included in a second connector. 28.The power distribution apparatus of claim 18, further comprising anequipment rack containing the bus bar assembly.
 29. The powerdistribution apparatus of claim 28, wherein the equipment rack includesa roof through which the power cable is routed.
 30. The powerdistribution apparatus of claim 28, wherein the equipment rack includesan uninterruptible power supply.
 31. The power distribution apparatus ofclaim 30, wherein the equipment rack includes a bypass switch.
 32. Thepower distribution apparatus of claim 30, wherein the equipment rackincludes a transformer.
 33. The power distribution apparatus of claim32, wherein the equipment rack includes a switch that is adapted toselectively couple the plurality of bus bars to an output of theuninterruptible power supply and an output of the transformer.
 34. Thepower distribution apparatus of claim 32, wherein the equipment rackincludes a plurality of bus bar assemblies.
 35. The power distributionapparatus of claim 18, wherein the bus bar assembly includes a pluralityof positions each adapted to receive a plug-in module.
 36. The powerdistribution apparatus of claim 35, further comprising a plurality ofplug-in modules each of the plurality of plug-in modules being installedin one of the plurality of positions.
 37. The power distributionapparatus of claim 18, further comprising secondary circuitry.
 38. Thepower distribution apparatus of claim 37, wherein the plug-in moduleincludes a current sensing device, and wherein the secondary circuitryis adapted for connection to an output of the current sensing devicewhen the plug-in module is installed in the bus bar assembly.
 39. Thepower distribution apparatus of claim 38, wherein the secondarycircuitry includes control circuitry.
 40. A method of installing a powerdistribution system in a facility, the method comprising acts of:obtaining a plurality of plug-in modules, each of the plug-in moduleshaving a housing containing a circuit breaker, a power cable having afirst end electrically coupled to the circuit breaker, and electricalcontacts coupled to the circuit breaker; and installing at least some ofthe plurality of plug-in modules in a power distribution assembly bysliding the plug-in modules into the power distribution assembly suchthat the electrical contacts of each of the plug-in modules areelectrically coupled to electrical conductors in the power distributionassembly.
 41. The method of claim 40, further comprising an act ofselecting a continuous current rating for each of the circuit breakersfrom a range of available continuous current ratings.
 42. The method ofclaim 41, wherein the housing is adapted to have a uniform sizeregardless of the current rating that is selected.
 43. The method ofclaim 40, wherein the circuit breaker is adapted for installation on aDIN rail.
 44. The method of claim 40, wherein the power distributionassembly includes secondary circuitry, and wherein the method furthercomprises an act of connecting circuitry included in at least one of theplurality of plug-in modules to the secondary circuitry.
 45. The methodof claim 44, wherein the at least one of the plug-in modules includes acurrent sensor, and wherein the act of installing includes an act ofconnecting an output of the current sensor to the secondary circuitry.46. The method of claim 44, wherein the act of connecting circuitryincluded in the plug-in module to the secondary circuitry includes anact of connecting circuitry included in the at least one of the plug-inmodules to control circuitry adapted to control an operation of thecircuit breaker included in the at least one of the plug-in modules. 47.The method of claim 44, wherein the act of connecting circuitry includedin the plug-in module to the secondary circuitry includes an act ofconnecting circuitry included in the at least one of the plug-in modulesto circuitry adapted to provide an indication of a status of the atleast one of the plug-in modules.
 48. The method of claim 40, furthercomprising an act of installing a power distribution assembly in a firstequipment rack.
 49. The method of claim 48, wherein the equipment rackincludes a roof, and wherein the method further comprises an act ofrouting at least one power cable out the roof.
 50. The method of claim48, further comprising an act of coupling at least one power cable to asecond equipment rack.
 51. The method of claim 50, wherein the powercable includes a second end electrically coupled to a connector, andwherein the method further comprises an act of coupling the connector toa connector associated with the second equipment rack.
 52. The method ofclaim 50, wherein the act of obtaining includes an act of obtaining aplurality of plug-in modules each having a length of power cable that isalready determined when the plug-in modules are obtained.